Subsurface Imaging: Scope and Applications

Imaging is the measurement of the spatial distribution of some physical property of an object by use of an instrument such as a camera, an optical or ultrasonic scanner, a microscope, a telescope, a radar system, or an X-ray machine. The spatial scale of the object may range from subnanometer to light years, as illustrated by the pictorial examples in Fig. 1.1-1. Numerous medical, biological, geophysical, oceanographic, atmospheric, and industrial applications exist, and each field has its tools, methods, and nomenclature. However, despite the wealth of applications and the breadth of spatial scales, a number of basic principles and methodologies are common among all imaging systems. This book highlights these principles, with an ultimate goal of introducing a unified framework for these broad applications.

Subsurface imaging (SSI) is the imaging of an object buried below the surface of a medium, such as soil, water, atmosphere, or tissue. The imaging process is mediated by some field, wave, or stream of particles that probe the medium, and is modified by the object before it is detected by a sensor, as illustrated in Fig. 1.1-2. A significant impediment is that the surface and the medium, and any clutter therein, also modify the probe (and possibly prevent it from reaching the object or the sensor). The imaging system must separate contributions made by the object from those made by the surface and volumetric clutter.